Conventional silicidation techniques employ nickel (Ni)/Pt as a sputter target. The Pt serves as a nickel silicide (NiSi) stabilizer and as an etch stop for a subsequent contact etch. After the NiSi formation sequence of sputtering Ni/Pt and performing a first rapid thermal anneal (RTA), a sulfuric acid-hydrogen peroxide mixture (SPM) is applied to wet strip unreacted Ni. Since SPM fails to strip unreacted Pt, after a second RTA, concentrated Aqua Regia (1:4) (nitric acid (HNO3) plus hydrochloric acid (4HCl)) is employed to strip the unreacted Pt. The HCl yields chloride ions which react with Pt according to formula I to form chloroplatinate ion (PtCl6), which in turn is soluble and forms chloroplatinous acid (H2PtCl4).Pt4+(aq)+6Cl−(aq)→PtCl62−(aq)  Formula I
However, Pt-residuals may still be found on the wafer during processing of the nickel-platinum silicide (NiPtSi) contact electrodes, particularly in high volume manufacturing. The root cause for the residuals includes incomplete stripping of the platinum, a chemistry change, the chemical concentration, environmental conditions, tools, etc., of which some factors are not controllable. Such residuals can cause contact to contact or contact to gate shorts. Although it has been found that application of SPM at high temperatures, such as greater than 160° C., dissolves Pt-residuals, this is costly, may damage the underlying layers of NiPtSi contact electrodes, titanium nitride (TiN) high-k metal gate, silicon nitride (Si3N4) spacers, and silicon dioxide (SiO2) field oxide, and, therefore, is ineffective for high volume manufacturing.
A need therefore exists for methodology enabling a rework procedure to remove Pt-residuals from NiPtSi contact electrodes, without damaging underlying layers and while maintaining a high through-put.